1. Field of the Invention
The present invention relates to navigation devices. More particularly, the invention relates to a navigation apparatus configured for removably coupling with and providing navigational capabilities to a portable, handheld computing device such as a personal digital assistant or pocket PC.
2. Description of the Prior Art
Global positioning system (GPS) receivers and other navigational devices continue to grow in popularity and are used in many applications, including recreational activities and automobile and marine navigation. The global positioning system (GPS) is an electronic satellite navigation system which permits users to determine their position with respect to the Earth. Global positioning may be determined with a handheld GPS receiver which detects and decodes signals from a number of satellites orbiting the Earth. The signals from each of these satellites indicate the position of the satellite and the time at which the signals were sent. To decode the satellite signals, known as spread spectrum signals, and thereby calculate desired position and navigational data, a GPS receiver must first “find” or acquire the signals emitted from a minimum number of satellites. Once the receiver is “locked on” to the spread spectrum signals, the user's global position and other navigational data (e.g., velocity of movement) can be calculated.
A typical GPS unit includes (along with other components) a GPS receiver which receives satellite signals from a plurality of GPS satellites, resident memory in which cartographic data and other location information may be stored, a processor for determining the location of the unit as a function of the received satellite signals and for accessing and processing data and information in the memory, and a display for displaying the information along with an indication of the unit's location. The resident memory may be integral with the processor, memory chips coupled with the processor, or may include plug-in memory modules that fit within corresponding memory slots in the receiver. The processor retrieves information from the memory, for example, to display maps and routing instructions to permit a user of the GPS receiver to navigate to a desired location.
Portable, handheld computing devices such as personal digital assistants (PDAs) and pocket PCs also continue to grow in popularity. Such devices are compact and lightweight and therefore can be easily carried to allow users to quickly and easily retrieve and store phone numbers, schedules, notes, and other data, play computer games, and/or perform many other computing functions previously reserved for larger desktop or laptop computers.
With the continued popularity of both GPS devices and portable, handheld computing devices, combined portable GPS/computer units which perform many of the same functions as separate GPS units and handheld computing devices have been developed. Unfortunately, such combined units are typically larger and heavier than handheld computing devices alone and therefore defeat some of the portability advantages of these devices. Moreover, many people already own conventional handheld computing devices and do not wish to discard them for newer combined GPS/computer units.
To alleviate some of the limitations of combined GPS/computer units, peripheral GPS devices have been developed that plug in or otherwise connect with conventional handheld computing devices. These peripheral GPS devices can be used to provide some navigational capabilities to existing handheld computing devices and can be removed when not needed so as not to distract from the portable nature of the devices.
Unfortunately, known peripheral GPS devices also suffer from several limitations that limit their utility. For example, such devices are configured for coupling with a serial port of a handheld computing device. Most handheld computing devices have only one serial port, and once it is used to couple with a peripheral GPS device, it is no longer available for other purposes such as downloading information from a personal computer. Moreover, known peripheral GPS devices have limited processing power and little or no memory and therefore are unable to provide many enhanced navigational capabilities desired by users.